Heterocyclic isocyanates containing two ring nitrogen atoms

ABSTRACT

a-Pyridyl, a-pyrimidyl and a-pyrazinyl isocyanates which contain electronegative substituents in the ring are prepared by reacting the corresponding amino compounds with oxalyl chloride. Due to the high reactivity of the -NCO group these compounds are particularly useful as cross linking agents and modifiers for compounds containing Zerewitinoff-active hydrogen.

United States Patent von Gizycki et al.

[ HETEROCYCLIC ISOCYANATES CONTAINING TWO RING NITROGEN ATOMS [751 Inventors: Ulrich von Gizycki; Giinter Oertel,

both of Cologne-Flittard; Guenther Beck; Kurt Findeisen, both of Leverkusenv all of Germany [73] Assignee: Bayer Aktiengesellschaft,

Leverkusen Bayerwerk, Germany [22] Filed: June 6, I972 [21] Appl. No.: 260,088

Related US. Application Data [62] Division of Ser. No. l27.378. March 23. [97L [30] Foreign Application Priority Data Mar. 26, 1970 Germany .6 2014762 [52] US. Cl 260/2564 N; 260/775; 260/250 B;

260/250 BN; 260/288 R [51] Int. Cl C07d 51/42 [58] Field of SearchmH 260/2564 N, 251 R- 250 R.

[56] References Cited UNITED STATES PATENTS 3.46l.l49 8/]969 Hard} et al 260/453 {451 Nov. 11, I975 FOREIGN PATENTS OR APPLICATIONS 2.014.762 I0/l97l German) .l 260/250 R 764.895 3/l970 Belgium I, 260/250 R OTHER PUBLICATIONS KirkOthmer, Ed, Encyclopedia of Chemical Technology (2nd Ed. Interscience, 1963.

Nycz. Chemical Abstract, 77:1 l4358t (1972) of Diss, Ahslr. lntv B [972. 32( Il)' 6305.

von Gizycki et alt, Chemical Abstract 76:34282c. 1972 von Gizycki et al.. Chemical Abstracts 75:885625.

Primary E.\mninm'Donald G. Daus Assisum/ E.\'ummer-Ralph D. McCloud AHUHM), Agent, or FirmJ0seph C. Gil

[57] ABSTRACT a-Pyridyl, a-pyrimidyl and a-pyrazinyl isocyanates which contain electronegative substituents in the ring are prepared by reacting the corresponding amino compounds with oxalyl chloride. Due to the high reactivity of the NCO group these compounds are par ticularly useful as cross linking agents and modifiers for compounds containing Zerewitinoffiactive hydrogen.

7 Claims. No Drawings HETEROCYCLIC ISOCYANATES CONTAINING TWO RING NITROGEN ATOMS This is a division of application Ser. No. 127,378, filed Mar. 23, 1971.

This invention relates to organic isocyanates and more particularly to a new class of heterocyclic isocyanates and a method for their preparation.

Pyridines and analogues of pyridine substituted by isocyanate groups in the position adjacent the ring nitrogen have hitherto been unknown.

It is therefore an object of this invention to provide a-pyridal, a-pyrimidyl and a-pyrazinyl isocyanates which contain electronecative substituents in the ring. It is another object of tnis invention to provide apyridal, a-pyrimidyl and a-pyrazinyl isocyanates which contain electronegative substituents in the ring.

The foregoing objects and others are accomplished in accordance with the invention, generally speaking, by providing heterocyclic isocyanates, which contain a maximum of two ring nitrogen atoms, having the general formula R, A NCO wherein X is nitrogen or aEC-R,

radical, wherein R, is halogen, halogen alkyl, cyano or nitro; X is nitrogen or aEC-R radical, wherein R is halogen, halogen alkyl cyano or nitro; X is nitrogen or afEcR,

radical, wherein R is hydrogen, halogen, halogen alkyl aryl, alkyl, alkylene, aryl carbonyl, alkyloxy carbonyl, aryloxy carbonyl or halogen carbonyl; and R is the same as R, and together with R can form a condensed ring. The heterocyclic compounds of the invention are readily obtained by reacting a corresponding amino compound having the formula wherein X, X, X and R are as defined hereinabove, preferably in an inert organic solvent such as, for example, benzene, toluene or chlorobenzene, with at least 1, and preferably about 1.5 to about 3.5 mols of oxalyl chloride per mol of the amino compound. The reaction may be carried out at a temperature of from about to about 250C. and preferably at a temperature of from about 40 to about 180C. As a rule, the starting amine which may be dissolved in an inert solvent, is added dropwise to a boiling mixture of oxalyl chloride and inert solvent, and the resulting mixture maintained at the boil until the evolution of gas has ceased, in accordance with the following reaction NCO The reaction mixture is then separated by conventional distillation techniques to yield the corresponding isocyanate in a purified form.

Thus, according to the invention heterocyclic isocyanates, having a maximum of two ring nitrogen atoms, having the general formula x x R4 AN7 NCO in which X, X", X and R are as defined above, are prepared from an amino compound, having a maximum of 2 ring nitrogen atoms, having the general formula 3 B4 A /J NH N chlorocarbonyl-4,S,6-trichloro-a-aminopyridine, 3,4,5- ,6,7,8-hexachloro-a-aminoquinoline, 4,5,6-trichloro-2- aminopyrimidine, 4,5,6-trifluoro-2-aminopyrimidine, 4,6-dichloro5-dichloromethyI-Z-pyrimidine, 4,5,6- tricyano-Z-aminopyrimidine, 4,6-dibromo--nitro-2- aminopyrimidine, 4,6-difluOro-Z-aminopyrimidine, 4,- 6-dichloro-S-phenylcarbonyl-2-aminopyrimidine, 2,5,- 6-trichloro-4-aminopyrimidine, 2-dichloromethyl-5,6- dichloro-4-aminopyrimidine, 2-pentachloroethyl-5,6- dichloro-4-aminopyrimidine, 2-phenyl-3,6-dichloro-4- aminopyrimidine, 2,5,6-trifluoroand, 2,5,6-tribromo- 4-aminopyrimidine, 2-cyano-5,6-difluoro4- aminopyrimidine, 2,5-difluoro-4-aminopyrimidine, 2- fluoro-S,6-dichloro-4-aminopyrimidine, 2-cyano-5,6- difluoro-4-aminopyrimidine, 2,5-difluoro-4- aminopyrimidine, 2-fluoro5,6-dichloro-4- aminopyrimidine, 2,6-dichloro-5-nitro-4- aminopyrimidine, 2 phenylcarbonyl 5 trichloromethyl- 6-cyano-4-aminopyrimidine, trichloro-aminopyrazine, trifluoroaminopyrazine, 2,5-dichloro-6-trichloromethyl-3-aminopyrazine, 2,5-dibromo-6-phenyl-3- aminopyrazi ne, tris-( trichloromethyl )-aminopyrazine, 2-chloro-5,6-dicyano-3-arninopyrazine and the like.

Amino compounds corresponding to the above general formula which are substituted by chlorine in at least one a-position to a ring nitrogen atom are preferably used in the process according to the invention.

The heterocyclic isocyanates produced by the process of the invention are usually colorless, liquid or crystalline compounds and are highly sensitive to atmospheric moisture due to their extremely high reactivity.

The compounds of the invention are suitable for use in the production of optical brighteners and dyes, as reactive components for dyes, as cross-linking agents for plastics and as intermediate products for the preparation of plant protection agents and pharmaceutical preparations.

Those compounds which are substituted by chlorine in at least one a-position to a ring nitrogen atom are of particular interest. Monofunctional isocyanates of this type can be regarded as difunctional or polyfunctional compounds whose functional groups differ in their reactivity by virtue of the activated chlorine atoms in the a-position to the ring nitrogen atom.

The NCO group in these isocyanates is about ten times more reactive than conventional aliphatic and aromatic monoisocyanates and diisocyanates, and as a consequence can be reacted, for example, in an anhydrous medium with any low molecular weight and high molecular weight compounds containing Zerewitinoffactive hydrogen without any danger of promoting complete cross linking through the activated halogen in the initial reaction stage.

Low molecular weight or high molecular weight compounds modified in this way such as, for example, dyes, polyethers and polyesters containing amino groups or hydroxyl groups may then be cross linked in a section reaction stage by heat treatment or basic treatment with a low molecular weight or high molecular weight compound containing Zerewitinoff-active hydrogen atoms, accompanied by the elimination of hydrogen chloride.

Due to the high reactivity of the NCO group of the compounds prepared in accordance with the process of the invention a fairly wide range of compounds containing active hydrogen atoms may be modified as described hereinabove.

As a result, the heterocyclic isocyanates of the invention which are chlorine-substituted in the a-position to the ring nitrogen atom are superior to the diisocyanates frequently used for this purpose, and also to cross linking agents of the cyanuric chloride type, since they combine the properties of both the diisocyanates and cyanuric chlorides, without manifesting of the disadvantages in the first or second reaction stages as do the conventional types of compounds.

The invention is further illustrated but it is not intended that it be limited by the following examples in which all parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 Preparation of 3,4,5,6-tetrachloro-a-pyridyl isocyanate A solution of about 45 parts of 3,4,5,6-tetrachloro-aaminopyridine (W. 1. Sell and F. W. Dootson, J. Chem. Soc. (London) 73, 781 (1898)) in about 750 parts by volume of dry benzene is added dropwise at reflux temperature to a mixture of about parts of oxalyl chloride in about 400 parts by volume of benzene. The mixture is boiled under reflux until the evolution of gas has ceased. Distillation yields about 42 parts of the isocyanate of a boiling point of 101 to 102C. at 0.05 to 0.06 mm. Hg. The colorless distillate solidifies in the receiver.

EXAMPLE 2 Preparation of 4,5,6-trichloropyrimidyl-Z-isocyanate A solution of about 13 parts of 4,5,6-trichloro-2- aminopyrimidine (Scott J. Childress and R. L. MacKee, J. Am. Soc. 72, 4271 (1950)) in about 450 parts by volume of absolute benzene is added dropwise at reflux temperature to a mixture of about 20 parts of oxalyl chloride in about 100 parts by volume of absolute benzene. The mixture is boiled under reflux until the evolution of gas has ceased (about 2 hours). On distillation, about 11 parts of the isocyanate having a boiling point of to 91C. at 0.06 mm. Hg. are obtained. The colorless distillate solidifies in the receiver.

EXAMPLE 3 Preparation of 2,5,6-trichloropyrimidyl-4-isocyanate A solution of about 17 parts of 2,5,6trichloro-4- aminopyrimidine (H. Ackermann and P. Dussy, Helv. Chim. Acta. 45, 1683 (1962)) in about 450 parts by volume of absolute benzene is added dropwise at reflux temperature to a mixture of about 20 parts of oxalyl chloride in about parts by volume of absolute benzene. The reaction mixture is boiled under reflux until the evolution of gas has ceased (about 2 hours). On distillation, about 1 1 parts of the isocyanate having a boiling point of 81 to 82C. at 0.05 mm. Hg. are obtained in the form of a colorless liquid.

Preparation of the starting materials used in Examples 4 to 7 5,6-dichloro-2-pentachloroethyl-4-aminopyridine ammonia is introduced. After most of the solvent is distilled ofi', the reaction mixture is poured into ice water, the deposit filtered under suction, washed with water and dried. Recrystallization yields about 100 parts of the iEminopyridine having a melting point of about 174 The following compounds are similarly prepared c1 N I C s a-m1,

melting point: 207 C.

solvent: benzene Cl N l ,y 1 C1 N CCI;

melting point; 90C. to 9]C. solvent: petrolcum'ethcr melting point: 193C. to 194C. solvent: clioxanc Preparation of the 2-substituted-4,5,6- trichloropyrimidines used as starting compounds is described in Belgian Pat. No. 726,729.

EXAMPLE 4 Preparation of 5,6-dichloro-2-dichloromethyl-pyrimidyl-4-isocyanate A solution of about 20 parts of 5,6-dichloro-2- dichloromethyl-4-aminopyrimidine in about 350 parts by volume of absolute benzene is added dropwise at reflux temperature to a mixture of about 25 parts of oxalyl chloride in about 100 parts by volume of absolute benzene, and the reaction mixture is boiled under reflux until the evolution of gas has ceased (about 7 hours). After distillation, about 15 parts of the isocyanate having a boiling point of 93C. at 0.03 mm. Hg. are obtained in the form of a colorless liquid.

EXAMPLE 5 Preparation of 5,6-dichloro-2-trichloromethyl-pyrimidyl-4-isocyanate A solution of about 20 parts of 5,6-dichloro-2- trichlorornethyl-4-aminopyrimidine in about 150 parts by volume of absolute benzene is added dropwise at reflux temperature to a mixture of about 25 parts of oxalyl chloride in about parts by volume of absolute benzene, and the reaction mixture is boiled under reflux until the evolution of gas ceases (about 10 hours). After distillation, about 15 parts of the isocyanate which boils at about C. at 0.05 mm. Hg. are obtained in the form of colorless liquid which gradually solidifies in the receiver.

EXAMPLE 6 Preparation of 5,6-dichloro-2-pen tachloroethyl-pyrimidyl-4- isocyanate A solution of about 20 parts of 5,6-dichloro-2- pentachloroethyl-4-aminopyrimidine in about parts by volume of absolute benzene is added dropwise over a period of about 30 minutes at reflux temperature to a mixture of about 25 parts of oxalyl chloride in about 100 parts by volume of absolute benzene. The reaction mixture is further heated until the evolution of gas ceases (about 10 hours). The clear yellowish solution is distilled and yields about 15 parts of the isocyanate which boils at about 143 to 144C. at 0.1 mm. Hg. in the form of a colorless liquid which crystallizes in the receiver.

EXAMPLE 7 Preparation of 5,6-dichloro-2-phen yl-pyrimidine-4-isocyanate About 85 parts of dichloro-2-phenyl-4- aminopyrimidine are dissolved under heat in about 1500 parts by volume of hot benzene and the resulting solution added dropwise at reflux temperature to a mixture of about 100 parts of oxalyl chloride in about 500 parts by volume of absolute benzene over a period of about 1.25 hours. The reaction mixture is then further heated until the evolution of gas ceases (about 2 hours). The reaction product is distilled yielding about 90 parts of the isocyanate which boils at about 147 to 148C. at 0.1 mm. to 0.2mm. Hg. The isocyanate immediately solidifies in the receiver to form colorless crystals melting at about 90 to 92C.

EXAMPLE 8 Preparation of trichloro-isocyanate-pyrazine About 10 parts of trichloroaminopyrazine are dissolved in about 50 parts by volume of absolute benzene and the resulting solution is added dropwise to a boiling mixture of about 50 parts by volume of benzene and about 20 parts of oxalyl chloride over a period of about 45 minutes. The mixture is kept under reflux until the evolution of gas ceases (about 8 hours). After cooling. the mixture is filtered off from about one part of a crystalline deposit and the filtrate is concentrated by evaporation in a water jet vacuum. The colorless residue is distilled in a high vacuum, yielding about 7 parts of the isocyanate melting at 65 to 70C. and boiling at about 100C. at 0.07 mm. Hg.

Although the invention has been illustrated in considerable detail in the foregoing examples it is to be understood that such exemplification is solely for the purposes of illustration and that any of the components listed as suitable herein may be freely substituted for their counterparts and that one skilled in the art may make many variations without departing from the spirit and scope of the invention.

What is claimed is:

l. A heterocyciic isocyanate having only two ring nitrogen atoms and having the formula:

R /L NCO N wherein NCO 3. An a-pyrimidyl isocyanate of claim 1 having the formula C1 NCO 4. An a-pyrimidyl isocyanate of claim 1 having the formula (:1 mco 5. An a-pyrimidyl isocyanate of claim 1 having the formula C l C NCO 6. An a-pyrimidyl isocyanate of claim 1 having the formula Ct Cl NCO c ci,

7. An a-pyrimidyl isocyanate of claim 1 having the formula Cl NCO 

1. A HETEROCYCLIC ISOCYANATE HAVING ONLY TWO RING NITROGEN ATOMS AND HAVING THE FORMULA:
 2. An a-pyrimidyl isocyanate of claim 1 having the formula
 3. An a-pyrimidyl isocyanate of claim 1 having the formula
 4. An a-pyrimidyl isocyanate of claim 1 having the formula
 5. An a-pyrimidyl isocyanate of claim 1 having the formula
 6. An a-pyrimidyl isocyanate of claim 1 having the formula
 7. An a-pyrimidyl isocyanate of claim 1 having the formula 